Writing of the season started on or before May 2011.[53]According toAndy Ristaino, by February 2012, the season had been written, storyboarded and approved.[54]The season will see the premiere of the 100th episode of the series, "The Hard Easy" (previously titled "Prince Huge"). Adam Muto reported that characters not seen since Season 1 will return, with TheEarl of Lemongrab,Magic Man,The Lich,Marceline's fatherandNEPTRbeing confirmed to return. Adam Muto said that bothBMOandMarceline's backstories will be also explored a bit more in this season.[55]The season will feature guest voices by Donald Faison, George Takei, Erik Estrada, Andy Milonakis, Emo Phillips, Bobcat Goldthwait and Susie Essman.[51]There will be two-part episodes in this season.Jeremy Shadaalso mentioned that Marceline and Ice King will sing together.[56]